This invention relates to an apparatus for storing a predetermined amount of electrical energy in a capacitor bank to be supplied to a strobe lamp. Strobe lamps typically comprise a glass bulb in which there are are two power electrodes, a triger electrode, and a gas which when ionized generates light of high intensity. A high electrical potential is placed across the two power electrodes, and when firing of the lamp is desired, a firing pulse will be applied to the trigger electrode. This firing pulse will ionize the gas sufficiently to allow current to flow between the two power electrodes with the result that the strobe lamp is flashed. Energy for this type of lamp generally is stored in a bank of capacitors placed in parallel with the lamp.
The capacitor bank will undergo significant changes in capacitance both as a result of aging and as a result of variations in ambient temperature. These capacitance changes are particularly troublesome in aircraft strobe lamp systems where variations in ambient temperature are likely to be pronounced. If no compensation is made for such capacitance variations, the capacitor bank will at times store and supply an excessive amount of energy to the strobe lamp and thus decrease the life span of the lamp. Strobe lamp intensity will also vary noticeably and this may be objectionable.
In the past, the energy stored in the capacitor bank has been approximated as a function only of the voltage across the capacitor bank; this voltage was monitored and compared against a predetermined voltage level in order to determine when the desired amount of energy was stored. A device using this technique is shown in U.S. Pat. No. 3,868,562, issued Feb. 25, 1975. Such an approach is acceptable only where the capacitance of the storage bank does not vary.